The invention relates to improvements in methods of and in apparatus for manipulating webs or strips, especially running webs or strips of wrapping material in machines of the tobacco processing industry. More particularly, the invention relates to improvements in methods of and in apparatus for subdividing a running web or strip, e.g., a web of so-called tipping paper, into discrete web portions or sections (the so-called uniting bands) which are to be draped around neighboring ends of groups of coaxial rod-shaped articles to convert such groups into composite rod-shaped articles. Typical examples of composite rod-shaped articles are filter cigarettes wherein a plain cigarette of unit length and a filter plug or filter mouthpiece of unit length are joined end-to-end by an adhesive-coated uniting band of cigarette paper, artificial cork or any other suitable wrapping material.
Apparatus of the present invention can be utilized with advantage in or in conjunction with filter tipping machines which cooperate with cigarette making machines and with filter rod making machines to turn out filter cigarettes, filter cigars or analogous composite rod-shaped articles of the tobacco processing industry.
A modern filter tipping machine comprises a magazine for a supply of filter rod sections of several times unit length, a conveyor system which supplies plain cigarettes of unit length from a so-called maker, a receptacle for a reel of convoluted web of filter tipping material, a system for subdividing filter mouthpieces of multiple unit length into filter mouthpieces or filter plugs of double unit length and for converting such filter plugs into a single file of parallel articles, a system of drums which assemble discrete filter plugs of double unit length and pairs of plain cigarettes of unit length into groups of three coaxial rod-shaped articles (with the filter plug located between the two cigarettes), a paster which provides one side of the web with a film of a suitable adhesive, a mechanism for dividing the running adhesive-coated web of wrapping material into discrete uniting bands, a system which drapes successive uniting bands around the filter plugs and the adjacent ends of the respective pair of plain cigarettes to convert such groups into filter cigarettes of double unit length, and a cutter which subdivides successive filter cigarettes of double unit length into pairs of filter cigarettes of unit length.
It is further customary to provide the web of tipping paper with suitably distributed perforations which permit the inflow of cool atmospheric air into the column of tobacco smoke flowing into the smoker's mouth. Reference may be had, for example, to U.S. Pat. No. 4,281,670 (granted Aug. 4, 1981 to Heitmann et al. for "APPARATUS FOR INCREASING THE PERMEABILITY OF WRAPPING MATERIAL FOR ROD-SHAPED SMOKERS' PRODUCTS"). The disclosure of this patent is incorporated herein by reference. Heitmann et al. disclose perforating units which operate with laser beams. The means for subdividing a running web into discrete uniting bands employs a standard suction drum which attracts the leader of the web to its peripheral surface, and a rotary cutter with axially parallel knives which sever a succession of uniting bands from the leader of the perforated web.
German patent application No. 41 22 273 A1 of Andreoli et al. (published Jan. 16, 1992) discloses a web severing apparatus wherein the knife or knives is or are replaced with a laser beam issuing from a source of coherent radiation which further serves to effect a desired perforating operation. Thus, the beam of coherent radiation issuing from the source is split into a first continuous partial beam (which is deflected by a rotary polygonal mirror to follow the moving web in the course of each severing operation), and into a second continuous beam which is directed toward the outlet of the tipping machine and is converted into a sequence of pulses which serve to provide the finished filter cigarettes with perforations in the converted (convoluted) uniting band and/or in the adjacent portion of the tubular wrapper of the plain cigarette. A drawback of such proposal is that the provision of a source of laser beams and of the aforementioned beam splitting, directing, deflecting and pulse generating means contributes significantly to the bulk, cost, complexity and sensitivity (proneness to malfunction) of the tipping machine.